3;  53 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION 

HONOLULU,  HAWAII 

Under  the  supervision  of  the 
UNITED  STATES  DEPARTMENT  OF  AGRICULTURE 


BULLETIN  No.  53 


THE  HAWAIIAN  TREE  FERN  AS  A 
COMMERCIAL  SOURCE  OF  STARCH 


BY 


J.  C.  RIPPERTON,  Chemist 


Issued  July,  1924 


„/>""•' 


<*\*M/ifc 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 

1924 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION,  HONOLULU 

LUnder  the  supervision   of   the   Office  of   Experiment   Stations, 
United  States  Department  of  Agriculture] 

E.  W.  Allen,  Chief,  Office  of  Experiment  Stations. 
Walteb  H.  Evans,   Chief,  Division  of  Insular  Stations, 
Office  of  Experiment  Stations. 


STATION  STAFF 

J.  M.  Westgate,  Agronomist  in  Charge, 
W.  T.  Pope,  Horticulturist. 
H.  L.  Chung,  Specialist  in  Tropical  Agronomy. 
J.  C.  Rippebton,  Chemist. 

R.  A.  Goff,  In  Charge  of  Glenwood  Substation  and  Exten- 
sion Agent  for  the  Island  of  Hawaii. 
Mabel  Greene,  Boys'  and  Girls'  Club  Leader. 


HAWAII 

AGR 

UNITED 

ICULTURAL    EXPI 
HONOLULU,  RAWi 

Under  the  supervision  of 
STATES  DEPARTMENT  OF 

:riment  station 
hi 

the 
AGRICULTURE 

53 

BULLETIN  No. 

Washington, 

D.    C. 

July  11, 

1924 

THE  HAWAIIAN  TREE  FERN  AS  A  COMMERCIAL 
SOURCE  OF  STARCH 


J.  C.  Ripperton,  Chemist 


CONTENTS 


Page 

Introduction 1 

Botanical  description 2 

Occurrence  in  Hawaii 3 

Studies    of   methods    of   propagation 


Page 

Chemical  composition  of  the  core 9 

Physical      properties      of      tree-fern 

starches 10 

Starch  making  from  the  tree  fern 13 


and  growth 3   I    Summary 15 


INTRODUCTION 

Many  generations  ago  the  natives  of  Hawaii  discovered  the  value 
of  the  tree  fern  as  a  source  of  food.  They  found  that  they  could 
use  the  tree  fern  in  place  of  the  taro  and  the  sweet  potato,  which 
constituted  their  favorite  and  staple  food  crops;  and,  likewise,  that 
they  could  live  indefinitely  upon  a  diet  of  tree  fern  and  wild  game 
when  they  were  defeated  in  battle  and  driven  from  the  seashore  to 
the  mountains.  Usually,  they  stripped  the  trunk  of  the  bark1  and 
baked  the  starchy  core  in  an  underground  oven.  It  is  not  un- 
likely that  the  natives  obtained  starch  from  the  tree  fern,  since  they 
were  familiar  with  the  art  of  extracting  it  from  the  arrowroot. 

Many  attempts  have  been  made  within  recent  years  to  produce 
tree-fern  starch  on  a  commercial  scale.  None  of  these  proved  suc- 
cessful, however,  due  to  insufficient  capital  for  the  proper  develop- 
ment of  the  product,  until  1920  when  tree-fern  starch  was  success- 
fully manufactured  and  appeared  on  the  local  markets  in  a  form 
suitable  for  use  as  food  and  for  laundry  purposes. 

Although  some  feared  that  the  new  industry  would  soon  destroy 
the  beautiful  tree-fern  forests,  the  Hawaii  Experiment  Station  re- 
ceived many  requests  to  aid  in  developing  it.  To  satisfy  those  who 
looked  unfavorably  upon  the  industry,  the  station  made  a  pre- 
liminary investigation  to  determine  the  effect  on  the  forests  and  on 
water  conservation  of  cutting  over  tree-fern  areas.     As  a  result  of 

1  In  this  publication  the  word  "  bark  "  is  used  to  describe  all  that  portion  of  the  tree- 
fern  trunk  except  the  central  starch-containing  core. 

94678—24 1 


2  BULLETIN  53,  HAWAII  EXPERIMENT  STATION 

the  investigation,  it  was  found  that  even  a  considerable  thinning  of 
the  ferns  for  starch  production  is  not  noticeable.  The  tree  fern 
falls  to  the  ground  of  its  own  accord^  or  is  easily  pushed  over,  upon 
reaching  maturity,  and  since  only  the  mature  trees  are  utilized  for 
starch  making,  relatively  few  trees  per  acre  would  be  cut  for  this 
purpose. 

A  rather  extended  program  of  work  was  therefore  outlined,  (1) 
to  determine  the  feasibility  of  planting  tree  ferns  on  cut-over  areas 
for  the  establishment  of  permanent-producing  areas,  and  (2)  to  make 
a  study  of  the  properties  and  uses  of  tree-fern  starch.  When  it  was 
found  that  the  rate  of  growth  of  the  tree  fern  is  too  slow  to  make 
it  commercially  practicable  to  replant  the  fern  and  the  necessity 
of  building  roads  and  fences  to  get  the  necessary  raw  material  be- 
came apparent,  hopes  were  abandoned  of  establishing  the  industry 
on  a  large  and  permanent  basis  in  Hawaii.  It  is  not  unlikely,  how- 
ever, that  the  industry  might  be  made  a  permanent  one  under  the 
economic  conditions  existing  in  other  tropical  countries  in  which  cer- 
tain species  of  the  tree  fern  are  indigenous. 

This  bulletin,  reporting  the  results  of  certain  observations,  to- 
gether with  data  on  the  Hawaiian  tree  fern  as  they  apply  to  its  use 
as  a  source  of  starch,  has  been  prepared  because  of  the  scientific 
interest  which  the  industry  has  aroused  and  because  of  the  potential 
importance  of  the  tree  as  an  emergency  crop  for  the  island  popula- 
tion in  case  of  interruption  of  shipping. 

BOTANICAL  DESCRIPTION 

Rock  2  lists  eight  species  of  Cibotium,  two  occurring  in  Guatemala, 
one  in  southern  Mexico,  one  in  the  monsoon  districts  of  east  Asia, 
one  in  the  Philippines,  and  three  that  are  peculiar  to  the  Hawaiian 
Islands.  The  following  botanical  description  of  the  two  most  im- 
portant species  in  Hawaii  may  be  of  interest.3 

Cibotium  menziesii. — *  *  *  Stipes  green,  stout,  with  a  ventral  and  two 
lateral  furrows,  tuberculate  and  shaggy  at  the  base  with  a  straightish  and  long 
brownish-yellow  glossy  pulu  which  changes  higher  up  into  stiff,  long  blackish 
hair,  and  as  such  often  covers  the  entire  stipes;  frond  with  stipes  18  to  36 
dcm.  or  more  long  and  9  to  15  dcm.  or  more  broad,  pyramidal-oblong,  coriaceous, 
naked  underneath  or  sometimes  with  minute  furf uraceous  dots ;  the  rhachis 
asperous  with  scattering  tubercles :  pinnae  with  a  stipe  of  25  to  50  mm.,  oblong, 
4.5  to  7.5  dcm.  long,  bearing  18  to  24  pairs  of  free  pinnules  besides  the  pinna- 
tifid  apex;  most  pinnules  shortly  stipitate,  linear  lanceolate,  acute,  cut  half- 
way or  more,  often  to  the  rhachis  at  the  base,  into  oblong  rounded  or  entire 
segments,  which  are  separated  by  broad  sinuses;  veinlets  very  prominent, 
simple  or  forked;  sori  8  to  14  on  a  lobe,  also  fringing  the  sinus.  Involucre 
corneous,  large,  a  little  more  than  1  mm.  to  nearly  3  mm.  in  width,  the  outer 
valve  fornicate  and  large,  the  inner  flat  and  narrower. 

C.  chamissoi. — *  *  *  Stipes  12  to  24  dcm.,  brownish,  smooth,  clothed  at 
the  base  with  a  pale  fawn-colored  lustreless,  matted  or  cobwebby  pulu,  fur- 
f uraceous  or  naked  above;  frond  12  to  24  dcm.  long,  chartaceous,  the  under 
face  green  or  dull  glaucous  and  generally  covered  with  a  pale  cobwebby  pubes- 
cence ;  lowest  pinnse  4.5  to  7.5  dcm.  long,  with  24  to  28  pairs  of  pinnules,  these 
shortly  stipitate,  linear  lanceolate  12.5  to  15  cm.  by  16  to  20  mm.  acute,  the 
lower  ones  cut  to  near  the  rhachis  into  oblong,  straightish,  rather  obtuse  seg- 
ments with  narrow  sinuses,  the  basal  segments  entire  and  not  deflected; 
veinlets  little  prominent;  sori  8  to  14  to  a  segment,  the  involucre  small  about 
1  mm.  wide,  chartaceous. 

2  Rock,  J.  F.     The  Indigenous  trees  of  the  Hawaiian  Islands,  p.  89. 

5  Rock,  J.  F.     The  indigenous  trees  of  the  Hawaiian  Islands,  pp.  91-93. 


HAWAIIAN  TREE  FERN  AS  A  SOURCE  OF  STARCH  6 

Hillebrand4  lists  another  species,  C.  glaucum,  but  states  that  it 
is  rather  rare. 

Clbotlum  chamissoi,  or  "  Hapu  "  as  it  is  popularly  known,  is  easily 
recognized  by  its  yellow  pulu  or  hair  and  its  comparatively  short, 
stocky  growth.  In  many  forests  it  constitutes  more  than  50  per 
cent  of  the  entire  tree-fern  growth.  The  trunk  sometimes  attains  a 
height  of  16  feet,  but  usually  does  not  exceed  10  feet.  The  diameter 
of  the  trunk  is  usually  8  to  12  inches.  (PL  I,  fig.  1.)  C.  menzitsii. 
or ;;  Hapu  Iii,"  is  distinguished  by  the  brownish  or  blackish  pulu  which 
covers  the  stipes  and  fills  the  crown.  Occasionally  it  attains  a  height 
of  40  feet  and  frequently  a  diameter  of  3  feet.  (PI.  I,  fig.  2.) 
Another  species,  commonly  known  as  the  "  Men,"  is  easily  recognized 
in  the  Hilo  district  by  its  very  slender  trunk,  smaller  fronds,  dull, 
lusterless,  rather  scant,  yellowish-brown  pulu,  and  nearly  naked 
stipes.  (PL  I,  fig.  3.)  The  "Amau"  (Sadleria  cyatheoides). 
although  a  different  genus  of  tree  fern,  is  also  of  interest  since  it  is 
exceedingly  common  in  occurrence  and  has  a  starchy  core. 

OCCURRENCE  IN  HAWAII 

The  tree  fern  is  found  in  all  parts  of  Hawaii  where  there  is  an 
annual  rainfall  of  100  inches  or  more.  It  grows  on  nearly  all  the 
mountains,  but  occurs  in  dense  forests  only  on  the  islands  of  Kauai 
and  Hawaii.  On  Kauai  the  forests  are  too  inaccessible  to  be  of 
importance  for  starch  production,  but  on  Hawaii  they  occur  in  al- 
most unbroken  stretches  from  sea  level  to  an  elevation  of  6,000  feet 
or  more.  These  long  stretches  are  reached  both  by  rail  and  auto- 
mobile roads  running  from  Hilo  to  the  Kilauea  Volcano.  The  wind- 
ward slopes  of  the  Manna  Kea  and  Mauna  Loa  Mountains  are  one 
continuous  tree-fern  forest,  the  belt  extending  from  the  Puna  dis- 
trict to  the  Hamakua  district  being  about  10  miles  wide  and  40  miles 
long.  In  general  it  is  estimated  that  there  are  400.000  acres  of  tree- 
fern  forests  on  the  island  of  Hawaii  alone.  A  very  large  part  of 
this  area  is  within  the  forest  reserve  or  on  Government -owned  lands, 
from  which  it  is  illegal  to  cut  the  tree  fern.  There  are,  however, 
many  thousands  of  acres  of  privately  owned  land  on  the  island  of 
Hawaii,  which  in  its  present  state  is  of  little  value  because  the 
dense  growth  of  tree  ferns  unfits  it  for  pasture  and  the  heavy  cover- 
ing of  leaf  mold  keeps  the  soil  too  wet  for  general  agricultural  pur- 
poses. The  owners  of  these  lands  regard  the  tree  fern  as  a  pest  and 
would  welcome  any  means  of  removing  it. 

STUDIES  OF  METHODS  OF  PROPAGATION  AND   GROWTH 

It  was  felt  that  before  the  tree-fern  starch  industry  could  be 
established  on  a  large  scale  in  Hawaii  some  feasible  method  must 
be  found  for  providing  a  permanent  source  of  the  raw  material. 
Many  of  the  tree-fern  areas  are  hard  to  reach,  and  it  is  almost  im- 
possible to  secure  the  raw  material  at  any  great  distance  from  the 
established  roads  because  of  the  rough  topography  and  the  heavy 
leaf  mold.  Moreover,  the  cost  of  getting  the  raw  material  from  the 
depths  of  the  forest,  when  the  supply  adjacent  to  the  highway  became 
exhausted,  would  reach  a  prohibitive  figure. 

*  Hillebrand.   Wm.     Flora  of  the  Hawaiian  Islands,  p.   347. 


4  BULLETIN  53,  HAWAII  EXPERIMENT  STATION 

The  possibility-  of  securing  a  large  tract  of  tree-fern  forest  for  the 
establishment  of  a  permanent  starch-producing  area  was  therefore 
considered.  Such  an  area  would  have  to  be  strongly  fenced  to  keep 
out  cattle  and  hogs,  and  roads  would  have  to  be  built  at  intervals, 
with  subsidiary  donkey  trails,  to  permit  of  the  tree-fern  logs  being 
carried  out.  The  purchase  c'f  such  a  tract  would  be  feasible  if  it 
could  be  shown  that  the  tree-fern  growth  could  be  successfully  main- 
tained by  natural  methods  of  propagation,  or  by  planting  cuttings 
from  different  parts  of  the  fern,  thus  assuring  a  permanent  and  in- 
creasing supply  of  readily  accessible  raw  material.  It  was  therefore 
decided  to  learn  whether  parts  of  the  tree  fern  could  be  successfully 
planted  on  cut-over  areas,  and  whether  the  rate  of  growth  would  be 
sufficiently  rapid  to  justify  the  cost  entailed  in  establishing  and 
maintaining  such  an  area. 

The  first  step  in  the  solution  of  the  problem  seemed  to  be  the 
acquisition  of  a  detailed  knowledge  of  the  character  and  habits  of 
the  tree  fern.  Since  the  literature  was  found  to  contain  only  certain 
botanical  descriptions,  a  series  of  observations  was  begun  of  its  nat- 
ural methods  of  propagation  and  growth. 

NATURAL  METHODS  OF  PROPAGATION 

The  tree  fern  reproduces  itself  in  two  general  ways — (1)  by  spore 
germination  (PL  II.  fig.  1)  and  (2)  by  lateral  shoot  development 
(PL  II,  fig.  2).  The  spores  are  borne  on  the  underside  of  the  fronds. 
Old  tree-fern  trunks  and  moss  furnish  excellent  seed  beds  for  spore 
germination,  and  land  that  is  undisturbed  by  cattle  and  wild  hogs 
is  frequently  literally  covered  with  the  tiny  ferns.  Their  growth 
is.  however,  very  slow. 

Propagation  by  lateral-shoot  development  on  the  trunks  of  ma- 
ture trees  is  much  more  rapid  than  by  spore  development.  One  to 
three  such  shoots  are  found  about  each  tree  in  varying  stages  of 
development  in  the  native  forests.  These  increase  to  as  many  as  15 
when  the  tree  fern  has  been  injured,  or  the  soil  about  it  trampled 
upon  by  animals.  The  shoots  begin  to  develop  when  the  parent 
tree  ceases  to  grow  or  falls  to  the  ground.  It  is  not  uncommon  to 
find,  even  on  young,  vigorous  trees,  one  or  two  shoots  which  are 
almost  as  large  as  the  parent.  The  shoot  soon  establishes  its  own 
root  system  and  in  a  short  time  becomes  independent  of  the  original 
fern.  The  crown  continues  to  grow  after  the  tree  has  fallen,  the 
fronds  gradually  turn  in  a  vertical  direction,  another  root  system 
is  established  at  the  new  base,  and  growth  proceeds  almost  unin- 
terruptedly. 

PLANTING   TREE    FERNS 

It  is  a  well-established  fact  that  tree  ferns  can  be  successfully 
propagated  from  crowns  and  lateral  shoots  which  spring  from 
the  trunk,  as  well  as  from  spores,  but  since  the  entire  inner  core 
of  the  trunk  is  used  for  starch,  planting  would  not  be  feasible  if 
sections  of  the  trunk  were  necessary  for  the  production  of  new 
growth:  and  it  was  not  known  whether  the  undeveloped  lateral 
shoots  which  are  found  on  the  average  tree  would  develop  if  re- 
moved  from  the  trunk.     Three  experimental  plats  were  therefore 


Bui.   53.    Hawaii    Agr.    Expt.   Station 


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Plate  II 


Fig.  !. — Natural  Propagation  from  Spores.  An  Old  Tree-Fern 
Trunk  Literally  Covered  with  Tiny  Tree  Ferns.  The  Spores 
Are  Found  on  the  Underside  of  the  Mature  Fronds 


Fig.  2. — Crowns  and  Lateral  Shoots  Used  for  Propagation 
Experiments 


HAWAIIAN  TREE  FERN  AS  A  SOURCE  OF  STARCH  5 

established  at  different  altitudes  for  the  purpose  of  determining  the 
feasibility  of  planting  the  tree  fern  for  starch  production.  These 
experiments  were  carried  on  at  the  following  places: 

(1)  Volcano  plat  (3,500  feet  elevation)  on  the  McKenzie  ranch,  at 
29  Miles,  Volcano  Road.  This  plat  is  adjacent  to  the  forest  re- 
serve on  windward  Hawaii.  It  is  used  as  a  pasture  and  contains  a 
scattered  growth  of  tree  ferns.  The  experiment  was  made  here  to  de- 
termine whether  the  tree  fern  could  be  successfully  planted  on  areas 
that  had  been  denuded  of  their  original  growth  and  on  which  there 
was  no  shade. 

(2)  Glenwood  plat  (2,000  feet  elevation),  located  2  miles  above 
Glenwood  on  the  Volcano  Road.  This  plat  was  selected  because  it  is 
in  the  midst  of  an  excellent  tree-fern  growth  and  is  easy  of  access. 
(PI.  Ill,  fig.  i.) 

(3)  Mill  plat  (2.200  feet  elevation),  located  4  miles  north  of  the 
Volcano  Road  at  18  Miles.  This  plat  is  in  an  area  now  being  cut 
over  for  starch  production.  It  represents  ideal  conditions  as  to 
shade,  soil,  and  the  like  under  which  the  tree  fern  would  be  planted. 

The  plantings  included  crowns,  and  large,  small,  and  medium 
sized  lateral  shoots  of  each  of  the  several  species.  Comparative 
plantings  were  made  to  determine  the  effect  on  growth  of  varying 
the  length  of  the  starch  core  attached  to  the  cuttings,  drying  the 
cut  surfaces  before  planting,  planting  at  different  depths,  in  different 
kinds  of  soil,  and  at  various  altitudes.  Since  this  work  was  dis- 
continued before  the  effect  of  these  various  factors  on  the  growth 
of  the  tree  fern  was  determined,  the  general  conclusions  of  the 
experiment  only  are  given. 

Under  true  forest  conditions,  such  as  existed  at  the  Mill  plat,  all 
crowns  and  lateral  shoots  were  successfully  propagated,  regardless 
of  variety,  size,  method  of  planting,  or  length  of  attached  starch  core 
(PL  III,  fig.  2).  Fully  70  per  cent  of  the  small,  undeveloped  shoots, 
which  had  been  detached  from  the  starch  core  of  the  parent  tree, 
grew  when  planted. 

The  plantings  made  in  the  open  pasture  on  the  Volcano  plat 
started  vigorous  growth  during  the  cool,  moist  winter  months,  but 
died  during  the  dry,  hot  summer  months.  Other  plantings,  made  in 
a  shaded  area  closely  adjacent,  lived  and  gave  results  similar  to 
those  obtained  at  the  Mill  plat. 

In  brief,  it  is  concluded  that,  under  true  forest  conditions,  an 
average  of  three  successful  plantings  or  sets  can  be  made  from  each 
felled  tree  fern ;  and  that  the  starch  core  of  the  parent  tree  need  not 
be  attached  to  the  plantings  or  sets.  It  seems  evident,  therefore,  that 
a  cut-over  area  could  be  successfully  replanted  without  interference 
with  starch  production,  and  that  the  density  of  growth  could  be 
gradually  increased  to  a  maximum. 

METHODS   OF   GROWTH 

In  order  to  determine  how  fast  the  tree-fern  trunk  grows,  it  was 
necessary  to  learn  the  nature  and  method  of  its  growth.  For  this 
purpose  a  study  was  made  of  the  lateral  growth  of  the  trunk,  the 
vertical  growth  within  the  trunk,  growth  at  the  base  of  the  trunk, 
and  growth  at  the  top  of  the  trunk. 


BULLETIN  53,  HAWAII  EXPERIMENT  STATION 


Fig.    1. — Graph    showing  the   spiral   arrangement 
of  tree-fern  fronds. 


The  lateral  growth  of  the 
starch  core  would  seem  to  be 
negligible  since  it  is  immedi- 
ately  surrounded  by  a  very 
hard,  brittle  covering  meas- 
uring one- fourth  to  one-half 
inch__in  thickness,  and  appar- 
ently is  incapable  of  further 
growth  or  expansion.    In  five 
out  of  eight  trees  the  starch 
core  was  found  to  be  appre- 
ciably larger  at  the  top  than 
at  the  bottom  of  the  trunk, 
which  shows  that  as  the  tree 
fern  grows  from  a  small  lat- 
eral shoot  or  spore  to  a  large 
size,    the    core    grows    corre- 
spondingly larger  at  the  top 
only ;  and  that  the  part  first 
formed  does  not  increase  in 
diameter.     Many    trees     are 
found    in    which    the    starch 
core  tapers  almost  to  a  point 
at    the    base.     Trees    grown 
from  very  large  lateral  shoots 
show   little   tapering   of   the 
core,  and  trees  resulting  from 
the    turned-up    crown    of    a 
large  fallen  tree  show  none 
at   all.     It   is   true   that   the . 
gross    diameter   of   the   tree, 
especially  of  the  species  Cibo- 
tium  menziesii,  increases  with 
the  growth  of  the  tree,  but 
this  increase  is  due  entirely 
to  the  increase  in  abundance 
of  the  air-feeding  roots  mak- 
ing up  the  outer  bark  of  the 
tree. 

That  there  is  no  vertical 
growth  within  the  trunk, 
except  at  its  apex,  is  shown 
by  the  fact  that  the  vertical 
distance  between  frond  pits 
on  the  same  spiral  is  the 
same  regardless  of  whether 
the  measurements  are  made 
at  the  bottom  or  at  the 
top  of  the  trunk.  This 
vertical  distance  would  show 
a     gradual     decrease     from 


HAWAIIAN  TREE  FERN  AS  A  SOURCE  OF  STARCH  7 

bottom  to  top  if  there  were  an  appreciable  growth  within  the 
trunk. 

Many  species  of  monocotyledonous  trees  show  an  increase  of 
growth  at  the  base  of  the  trunk,  as  is  frequently  evidenced  by  the 
dead  roots  which  are  found  covering  2  or  3  feet  of  the  base  of  the 
tree  trunk.  That  this  is  not  the  case  with  the  tree  fern  is  shown 
by  the  uniform  occurrence  of  pits  from  which  the  fronds  once  pro- 
truded along  the  entire  length  of  the  trunk.  It  would  seem,  there- 
fore, that  such  growth  in  the  tree-fern  trunk  is  negligible. 

The  method  of  growth  at  the  top  of  the  trunk,  however,  is  very 
striking.  In  the  early  spring  new  fronds  or  leaves  develop,  a  com- 
plete circle  of  new  fronds  averaging  five  in  number  emerging  from 
the  heart  of  the  crown  at  practically  the  same  stage  of  development 
(PL  IV,  fig.  1).  These  fronds  attain  full  size  within  about  three 
months  after  the  time  of  their  appearance  and  remain  on  the  tree 
from  18  to  2-i  months.  An  occasional  immature  frond  can  be  found 
on  the  tree  after  the  first  five  fronds  develop. 

METHOD   OF  DETERMINING  THE   RATE   OF   GROWTH 

"When  the  outer  bark  is  stripped  from  the  tree  fern,  or  when  an  old 
log  in  which  the  starch  core  has  decayed  is  split  open,  the  fronds  are 
observed  to  be  arranged  in  definite  spirals.  Figure  1  represents 
graphically  the  surface  of  a  tree-fern  log  from  which  the  outer  bark 
has  been  removed  to  disclose  the  location  of  the  frond  attachments, 
regarded  as  a  hollow  cylinder  cut  lengthwise  and  laid  out  flat.  The 
ellipses  represent  frond  pits  or  the  openings  in  the  bark  from  which 
the  fronds  protruded. 

A  number  of  different  spirals  are  apparent  in  the  diagram.  Among 
the  more  obvious  are  those  parallel  to  the  lines  o-d%  n-d\  and  m^a', 
respectively. 

The  arrangement  of  fronds  was  found  to  be  the  same  on  a  large 
number  of  stripped  tree-fern  logs,  and  the  spiral  combination  of  3,  5, 
and  8  fronds  could  readily  be  counted.  The  only  difference  noted 
was  in  the  direction  of  growth  of  each  spiral,  which  was  clockwise 
on  some  trees  and  counterclockwise  on  others. 

Since  probably  a  circle  averaging  five  fronds  is  developed  each 
spring,  each  of  the  five  spirals  would  seem  to  be  annually  represented 
by  one  frond.  If  this  were  true,  or  if  the  average  yearly  number  of 
fronds  per  tree  showed  little  variation  in  the  different  trees,  it  would 
be  necessary  only  to  measure  the  vertical  distance  between  two  frond 
pits  on  one  of  the  five  spirals  to  determine  the  annual  growth  of  the 
tree  (PI.  IV,  fig.  2). 

To  determine  the  correctness  of  this  assumption,  the  fronds  of  a 
number  of  trees  growing  at  different  altitudes  were  marked  with 
copper  tags  at  each  frond-setting  period  and  the  trees  were  visited 
once  a  year.  Usually,  it  was  not  difficult  to  distinguish  the  new 
fronds.  The  species  Hapu  (Cibotium  chamissoi) .  which  is  the  only 
one  used  to  any  extent  for  starch  production,  was  selected  for  this 
study. 


8 


BULLETIN  53,  HAWAII  EXPERIMENT  STATION 


Table  1  gives  the  annual  number  of  fronds  set  per  tree  during  four 
successive  years : 

Table  1. — Annual  number  of  fronds  set  per  tree  {Cibotium  chamissoi)   during 

four  successive  years 


Tree  No. 

Number  of  new  fronds  de- 
veloped 

Tree  Xo. 

Number  of  new  fronds  de- 
veloped 

1920 

1921 

1922    1923 

Aver- 
age 

1920 

1921  j  1922 

1923 

Aver- 
age 

Elevation,  S, 500  feet 
1.                 

5 
6 
4 
7 
5 
6 

5         3 

8         7 
.5         5 
7         5 

7  5 

8  5 
5         5 
7         5 
5         7 
5         4 

4.33 

7 

1. 

? 

Elevation,  2 ,200  feet 

5 
5 

5 
5 

6 
7 
6 
4 
6 
6 
5 

5 

.=;  2.1 

2 

3 

4. 67      3. 
6. 33      4. 

6         4 

6  1       5 

5          7 

5  '       3 

6  5 

5         5. 25 

4 

6          4. 75 

8 

5.67 
6.33 
5 
5.25 

5. 

?: 

8 

5          5. 5 

6 

5.75 

5          4. 5 

8. 

5 

4 

5.5 

6 
4.66    i 

Average 

5 

5.  25 

A  verage 

5.52 

j 

While  the  data  given  in  Table  1  do  not  conform  to  the  theory  that 
each  of  the  five  spirals  is  represented  annually  by  a  frond,  they  do 
verify  the  observation  that  the  average  annual  number  is  a  fraction 
over  five,  and  show  that  this  number  is  practically  the  same  regardless 
of  altitude. 

It  would  seem,  therefore,  that  the  rate  of  growth  of  the  tree  fern 
could  be  closely  determined  simply  by  measuring  the  vertical  dis- 
tance between  any  two  successive  frond  pits  of  the  same  spiral  and 
by  multiplying  this  distance  by  5.39  and  dividing  by  the  spiral  num- 
ber, that  is  by  3,  5,  or  8.  For  example,  if  this  distance  on  the  5 
spiral    averaged   4   inches,   the    yearly   vertical   growth   would    be 

5  39 

-^ — ,  or  4.31  inches;  or,  if  measured  on  the  3  spiral,  it  was  2.4 


4X 


5.39 


inches,  the  yearly  vertical  growth  would  be  2.4  X  -^ — ,  or  4.31  inches. 

o 

In  order  to  ascertain  the  average  vertical  distance  between  the 
frond  pits,  eight  trees  {Cibotium  chamissoi) ,  growing  near  the  Mill 
plat,  were  stripped  of  their  bark  and  measurements  were  made  of 
their  diameter,  length,  weight,  and  the  like.  These  data,  together 
with  the  rate  of  growth  as  computed  by  the  foregoing  method,  are 
given  in  Table  2 : 


Bui.   53,    Hawaii    Agr.    Expt.   Station 


Plate   III 


fFiG.   I. — Tree  Ferns  Grown  from  Crowns  at  Glenwood  Substation 

(Hawaii  i 


Fig.  2. — Tree-Fern  Hedge  Grown  from  Crowns 


Bui.   53,    Hawaii    Agr.    Expt.    Station 


Plate   IV 


*  c  » 

OC   W  * 

<   CO  ^ 

CQ  5  O  uj 

D  I  o: 

u  o 

I-    UJ  CO    — 

DI-)U. 

Oh  < 


HAWAIIAN  TREE  FERN  AS  A  SOURCE  OF  STARCH 

Table  2. — The  rate  of  growth  of  the  tree  fern  and  amount  of  starch  core  it 

produces  annually  l 


Tree  No. 

(a) 

Weight 

of  starch 

core 

(b) 

Length 

of  starch 

core 

Diameter  of  starch 
core 

(C) 

Vertical 

distance 

between 

successive 

fronds 

(d) 

Annual 
vertical 

growth  2 

(e) 

Esti- 
mated 
length 
of  time 
required 

for 
growth  3 

(0 

Starch 

core 

produced 

annually  4 

Top 

Bottom 

5-spiral 

1 

2.. 

3 

Pounds 
34.5 
64 
76 
87 
58.5 
72.5 
15 
11 

Inches 
66 
65 
80 

128 
72 

101 
33 
41 

Inches 
5.4 
7.3 
5.4 
4.8 
6.1 
5.7 
4.1 
3.8 

Inches 
3.8 
6.7 
6.1 
5.4 
4.1 
4.5 
4.5 
2.43 

Inches 
4.12 
4.06 
4 

4.57 
4.5 
3.49 
4.13 
3.41 

Inches 
4.44 
4.38 
4.32 
4.93 
4.85 
3.76 
4.45 
3.68 

Years 
14.9 
14.8 
18.5 
26 
14.8 
26.9 
7.4 
11.1 

Pounds 
2.31 
4.32 
4.11 

4 

5 

6 

3.35 
3.95 
2.7 
2.03 

8 

.99 

4.35 

2.97 

1  The  5-spiral  measurements  are  used  in  these  computations  because  the  coefficient  of  error  in  measure 
ment  is  less  than  in  case  of  the  3-spiral. 
*  c  multiplied  by  5.39,  divided  by  5. 

3  b  divided  by  d. 

4  a  divided  by  e. 

Table  2  shows  that  the  average  vertical  growth  of  the  tree  fern  is 
fairly  uniform  and  averages  4.35  inches  annually,  and  that  the  an- 
nual production  of  starch  is  subject  to  wide  variations  due  to  differ- 
ence in  diameter  of  the  starch  core.  The  annual  increment  in  starch 
core  averages  2.97  pounds. 

Sections  of  the  bark  of  a  large  number  of  trees  growing  at  vary- 
ing altitudes  were  slabbed  off  to  permit  of  measuring  the  distance 
between  successive  fronds  for  a  distance  of  about  1  foot.  The  data 
so  secured,  while  only  approximate,  would  seem  to  show  that  the  rate 
of  growth  of  the  tree  fern  is  practically  constant  between  sea  level 
and  an  altitude  of  3,500  feet.  Measurements  of  other  species  of  tree 
ferns  showed  that  they  make  about  the  same  rate  of  growth  as  does 
Cibotium  chamissoi. 

The  very  slow  rate  of  growth  of  the  tree  fern  brings  into  very 
serious  question  the  feasibility  of  planting  cuttings  of  different  parts 
for  starch  production.  It  would  require  at  least  20  years  to  grow 
a  tree  fern  of  sufficient  size  to  cut  for  starch,  since  it  has  been  found 
unprofitable  to  cut  trees  having  less  than  a  60-pound  starch  core. 
Twenty  years  is  a  rather  prohibitive  length  of  time,  especially  for  a 
small  industry,  to  wait  for  replanted  areas  to  furnish  new  material. 

As  a  result  of  the  investigations  it  was  concluded  that,  while  the 
tree  fern  can  be  successfully  planted  on  cut-over  areas,  its  rate  of 
growth  is  too  slow  to  make  such  a  procedure  advisable  under  present 
conditions. 

CHEMICAL  COMPOSITION  OF  THE  CORE 

Preparatory  to  analyzing  the  core  the  outer  fibrous  sheath  and  the 
hard  inner  bark  were  stripped  from  it.  The  yellowish-white  core 
was  then  shredded  and  the  nonreducing  and  reducing  sugars  were 
determined.    The  methods  of  analysis  recommended  by  the  Associa- 


10 


BULLETIN  53,  HAWAII  EXPERIMENT  STATION 


tion  of  Official  Agricultural  Chemists 5  were  employed  in  making" 
the  rest  of  the  analysis. 

The  results  are  given  in  Table  3.  which  includes  also,  for  purposes 
of  comparison,  the  chemical  composition  of  the  potato  and  edible 
canna.  both  of  which  are  grown  for  commercial  starch  production : 

Table  3. — Comparison  of  the  chemical  composition  of  the  tree-fern  core  with 
that  of  the  potato  and  edible  canna  tubers 


Constituent 


Tree 
fern  ( C.     Pntatn 
chamis-     Folato 

soi) 


Edible 


Constituent 


Tree 
fern  ( C.     p  t  t      Edible 

soi) 


Water. 

73.39 
.95 
.06 
1.04 

78.30 

2.20 

.10 

1.00 

72.62 

.98 

.11 

1.40 

Fiber 

N-free  extract..  .. 

1.57  : 

22.99  i 

.24 

3.99 

0.40 
18.00 

0  61 

Protein 

24  28 

Fat 

Xonr educing  sugars 

Reducing  sugars 

Ash... __ 

From  Table  3  it  will  be  seen  that  in  chemical  composition  the  core 
of  the  tree  fern  is  very  similar  to  the  ordinary  tuber  crops,  and,  as- 
might  be  expected,  it  contains  rather  large  amounts  of  reducing 
sugars.  In  view  of  the  peculiar  manner  of  growth  of  the  tree  fern, 
it  is  very  probable  that  the  sugar  content  varies  considerably  in  the 
different  sections  of  the  core  as  well  as  in  different  seasons. 

The  tree-fern  core  is  apparently  equal  to  other  starch  crops  as  a 
stock  feed.  It  is  eaten  readily  by  cattle  and  hogs,  probably  because 
of  its  high  sugar  content.  The  new,  tender  fronds  form  the  most 
important  part  of  the  forage  for  stock  pasturing  in  a  tree-fern  for- 
est ;  and  the  heart  of  the  trunk  is  also  eaten  when  it  can  be  reached. 
Were  it  not  for  the  prohibitive  amount  of  labor  required  to  split 
open  these  trunks,  the  tree  fern  undoubtedly  would  have  an  impor- 
tant place  among  the  stock  feeds  of  the  tree-fern  forest  districts. 

The  core  of  the  tree  is  not  palatable  as  human  food.  It  has  a 
peculiar  flavor  and  is  rather  fibrous.  The  tender,  undeveloped  fronds- 
are  sometimes  cooked  as  a  vegetable,  but  the  core  as  such  has  never 
become  of  practical  importance. 

PHYSICAL  PROPERTIES  OF  TREE-FERN  STARCHES 

Samples  of  starch  were  prepared  from  the  species  Hapu  (Cibotium 
chamissoi) .  Men  {Cibotium  sp.),  Hapu  Iii  or  Heii  (c7.  menziesii) T 
and  Amau  (Sadleria  cyatheoides)  .6  Microscopic  examination  and 
photomicrographs  were  then  made  of  each.  The  characteristics  of 
each  starch  as  they  appeared  when  magnified  220  diameters  were 
found  to  be  as  follows  : 

(1)   Hapu  (C.  chamissoi).     (PL  V,  fig.  1.) 

Size.  0.01  to  0.05  millimeter.  Varying  sizes  in  about  equal  proportion; 
shape,  irregular  oval,  occasionally  kidney-shaped,  in  large  sizes,  but  circular 
disks,  with  a  few  truncated  forms  in  the  small  sizes ;  hilum,  annular,  with  a  few 
longitudinal  rifts,  depressed,  usually  central  in  small  sizes ;  rings,  complete, 
very  distinct,  with  a  very  pronounced  ring  in  most  of  the  larger  granules  about 
midway  between  the  hilum  and  the  outer  edge;  polarizer,  very  brilliant  dark 
cross  at  central  axis. 


5  Methods  of  analysis  of  the  Association  of  Official  Agricultural  Chemists.  Sec.  VII, 
p.  71.     Revised  to  Nov.  1.  1919.  Washington,  D.  C,  1920. 

6  The  individuals  of  each  species  selected  for  these  samples  were  as  nearly  typical  speci- 
mens as  could  be  found.  No  botanical  identification  was  made  of  them,  since  they  exist 
in  comparatively  pure  strains,  and  no  difficulty  was  bad  in  differentiating  between  them. 


HAWAIIAN  TREE  FERN  AS  A  SOURCE  OF  STARCH  11 

Men  (Cibotium  sp.).     (PI-  V,  fig.  2.) 

Size.    0.01    to   n.Oo    millimeter    (Ion?   axis)  :    shape,    usually    elongated    disk 
in  the  large  sizes,  but  round  to  oval  in  the  small  sizes,  and  a  few  truncated 
and  kidney-shaped  in  all  sizes;  hilum,  usually  annular,   depressed,  eccentric; 
rings,  complete,  very  distinct ;  polarizer,  distinct  cross  at  hilum. 
(3)    Hapu  Iii  or  Heii  (C.  menziesii).     (PI.  VI,  fig.  1.) 

Size,  0.01  to  0.04  millimeter :   shape,   round  to  oval,  occasionally  truncated 
and  angular :  hilum.  annular,  central,  depressed ;  rings,  very  pronounced,  con- 
centric, complete :  polarizer,  very  distinct  cross  at  hilum. 
in  Amau  (Sadleria  cyatheoides).     (PI.  VI.  fig.  2.) 

Gore,  mostly  colloidal  dextrins.  with  starch  grains  of  extremely  minute  size. 
The  starch  can  not  be  separated  from  the  grated  mass  by  sedimentation ;  size, 
0.01  to  0.03  millimeter:  shape,  round  to  oval:  hilum.  usually  central,  annular, 
depressed ;  rings,  distinct  on  large  granules,  and  complete ;  polarizer,  well- 
marked  cross  at  hilum. 

The  illustrations  and  morphological  descriptions  show  that  the 
four  starches  possess  many  of  the  same  characteristics,  the  chief 
differences  being  in  size  and  shape.  Considered  from  the  standpoint 
of  the  physical  characteristics  of  the  starch  granules,  each  of  the 
four  species  could  be  used  for  starch  production.  As  a  matter  of 
fact,  the  starch  of  Cibotium  chamissoi  is  very  much  to  be  preferred 
to  that  of  the  other  three  species.  The  starch  of  both  C.  menziesii 
and  Men,  in  addition  to  being  of  small  diameter,  contains  such  large 
quantities  of  dextrins  and  other  colloidal  matter  as  to  make  the 
separation  of  the  starch  difficult.  The  starch  of  Sadleria  cyatheoides 
is  manifestly  unsuitable. 

VISCOSITY 

Since  the  viscosity  curve  of  a  starch,  when  transformed  by  boiling 
water  into  "  soluble  starch,"  is  useful  in  showing  its  general  proper- 
ties, determination  was  made  of  the  viscosity  of  tree-fern  starch, 
and  likewise  of  corn  and  arrowroot  starches  for  purposes  of  compari- 
son. The  method  of  procedure  was  as  follows:  Varying  amounts 
of  starch  were  weighed  into  100  cubic  centimeter  flasks  graduated  at 
80°  C.  with  10  cubic  centimeters  of  cold  water.  Boiling  water  was 
added  with  vigorous  shaking,  and  the  flasks  were  made  up  to  the 
mark  at  80°  C.  with  hot  water.  The  flasks  were  then  placed  in  boil- 
ing water  for  one  hour  without  agitation,  after  which  they  were 
quickly  cooled  to  80°  C.  with  as  little  agitation  as  possible,  and  the 
viscosity  was  determined  with  a  Saybolt  universal  viscosimeter  at 
that  temperature.  Duplicate  determinations  by  the  above  arbitrary 
procedure  agreed  with  fair  accuracy.  Any  variation  in  procedure, 
however,  caused  very  large  differences  in  the  result.  For  example, 
vigorous  shaking  during  cooking  decreased  the  viscosity  as  much  as 
50  per  cent.  Variations  in  temperature  and  time  of  cooking  also 
caused  appreciable  deviations.  The  results  are  graphically  given  in 
Figure  2. 

The  concentration  of  starch  solution  necessary  to  produce  a  defi- 
nite hydrogel  when  cooled  was  determined  by  pouring  10  cubic  cen- 
timeters of  the  hot  starch  solution  used  for  determining  the  viscosity 
into  test  tubes  one-half  inch  in  diameter.  The  tubes  were  placed 
in  water  at  about  18°  C.  and  allowed  to  remain  unagitated  for  one 
hour.  They  were  then  inverted.  The  minimum  concentration  neces- 
sary to  keep  the  mass  from  flowing  down  the  inverted  tube  was 
termed  its  ;*  gelling  strength."  The  gelling  strength  of  cornstarch, 
tree-fern  starch,  and  arrowroot  starch  was  found  to  be  4.25,  5,  and 
per  cent,  respectively. 


12 


BULLETIN  53,  HAWAII  EXPERIMENT  STATION 


The  above  data  on  viscosity  and  gelling  strength  bring  out  a  num- 
ber of  important  differences  among  the  starches.  The  concentra- 
tions necessary  to  cause  any  appreciable  increase  in  viscosity  were 
1.5  per  cent  of  arrowroot,  2  per  cent  of  tree  fern,  and  3  per  cent  of 
cornstarch.  Above  3  per  cent  the  curve  for  cornstarch  shows  a  very 
sharp  increase.  A  1-gram  increment  causes  an  increase  in  viscosity 
of  1  to  6,  whereas  a  like  increment  of  tree  fern  and  arrowroot  over 
the  concentrations  of  2  and  3  per  cent,  respectively,  causes  increases 
of  1  to  3.  As  the  concentration  increases,  the  tree  fern  and  corn- 
starch curves  practically  coincide.     The  arrowroot  curve,  although 


<J*J 

40 

f 

A 

g£2 

g22 

907 

3.5 
3LO 

as 

7 

* 

2D 
A5 

/.o 

& 

p~ 

0.5 

X 

Tig.  2. 


O      /     3     5     7    9     //    '3  /5  /7   /?  2/   23  25  27  29  31 
J//&CO&/7r"y  (M/A/C/T£:$)  AT  SO°C. 

— Comparison  of  the  viscosity  of  tree-fern  starch  and  other  commercial  starches. 


showing  greater  viscosity  than  that  of  the  tree  fern,  is  of  the  same 
general  nature. 

The  gelling  strengths  of  the  three  starches  were  in  the  opposite 
order  of  their  viscosities.  A  cornstarch  solution  with  a  viscosity  of 
8.75  formed  a  stiff  gel  when  cooled,  while  a  tree-fern  solution  re- 
quired a  viscosity  of  27  to  form  a  gel.  A  4  per  cent  arrowroot  solu- 
tion required  from  three  to  four  hours  to  pass  through  the  visco- 
simeter,  and  yet  a  5.25  per  cent  solution  was  necessary  to  form  a  gel. 

The  physical  qualities  and  appearance  of  the  three  are  likewise 
distinct.     Cornstarch  forms  a  tender,  clean-cutting,  definite  hydro- 


Bui.   53,    Hawaii   Agr.    Expt.   Station 


Plate  V 


Bui.   53,    Hawaii   Agr.    Expt.   Station 


Plate  VI 


Bui.   53,    Hawaii    Agr.    Expt.   Station 


PLATE    VII 


Fig.  I. — The  Starch  Core  of  the   Tree-Fern  Trunk,   Showing    the 

Large   Starch    Core   and   Thin    Bark   of  the   Cibotium   chamissoi 

Left  ,  and  the  Small  Starch  Core  and  Thick,  Dense  Bark  of  C. 

menziesii      Right  .     The    Former    Species    Is   the    One    Used    for 

Starch  Production 


Fig.  2. — An  80-Pound  Starch  Core  which 
Is  Ready  for  the  Shredder 


HAWAIIAN  TREE  FERN  AS  A  SOURCE  OF  STARCH  13 

gel,  while  the  other  two  starches  form  what  ma}'  be  termed  plastic 
gels,  or  simply  emulsions  having  a  very  high  viscosity.  The  former 
gel  is  greatly  affected  by  changes  in  temperature,  concentration, 
and  agitation,  whereas  the  latter  are  relatively  little  affected.  In 
appearance,  cornstarch  gel  is  opaque,  while  the  tree  fern  and  arrow- 
root gels  are  translucent. 

USES 

Tree-fern  starch  has  been  put  on  the  market  both  as  a  laundry 
starch  and  as  a  food.  It  is  claimed  that  only  half  the  concentration 
necessary  for  cornstarch  is  required  for  tree-fern  starch  for  laundry 
purposes.  Reference  to  Figure  2  bears  out  this  claim  to  some  extent, 
since  a  "2  per  cent  solution  of  tree-fern  starch  has  a  viscosity  equal 
to  3  per  cent  of  cornstarch,  which  is  about  the  usual  concentration 
used  for  laundering. 

Since  the  physical  properties  of  tree-fern  starch  are  simitar  to 
those  of  the  arrowroot,  the  former  is  being  advocated  as  a  substitute 
for  the  latter  for  invalids  and  infants.  Although  Figure  2  shows- 
it  to  have  less  strength  than  arrowroot  starch  has,  its  cost  is  only 
slightly  more  than  cornstarch  and  only  a  small  fraction  of  that  of 
arrowroot. 

In  Hawaii,  tree-fern  starch  is  largely  used  as  a  mixture  with  poi.7 
The  starch  is  simply  cooked  with  water  and  added  to  the  poi.  The 
cost  of  the  poi  is  materially  reduced  by  adding  the  starch  to  it,  its 
flavor  is  said  to  be  improved,  and  the  rate  of  fermentation  desirably 
retarded.  These  claims  are  substantiated  by  the  fact  that  practi- 
cally all  Hawaiian  institutions  using  poi  now  incorporate  tree-fern 
starch  with  it. 

As  a  food  substitute  for  cornstarch,  tree-fern  starch  is  not  gener- 
ally popular.  Figure  2  shows  that  at  a  concentration  of  4.25  per 
cent,  which  is  about  the  concentration  necessary  to  produce  a  corn- 
starch pudding,  tree-fern  starch  has  practically  the  same  strength. 
As  previously  noted,  however,  it  is,  like  arrowroot  starch,  some- 
what sticky  and  tenacious  in  comparison  with  cornstarch,  which  is 
tender,  and  clean-cutting. 

In  an  experiment  made  to  determine  the  digestibility  of  various 
raw  starches,  Langworthy  and  Deuel8  found  that  93.4  per  cent  of 
raw  tree-fern  starch  was  assimilated  by  the  human  system.  They 
also  found  that  tests  of  samples  of  the  feces  gave  no  distinct  blue 
color  with  iodin,  which  would  seem  to  indicate  that  "  the  proportion 
of  undigested  starch  was  very  small." 

Although  no  digestion  tests  have  been  conducted  with  the  cooked 
starch,  it  is  thought  that  its  digestibility  is  rather  high,  due  to  its 
large  granules  and  its  exceptionally  easy  conversion  into  soluble 
starch. 

STARCH  MAKING  FROM  THE  TREE  FERN 

If  the  trunk  of  any  of  the  different  species  of  tree  fern  is  cut 
crosswise,  it  will  be  found  to  contain  a  central  starch  core  of  3  to  10 
inches  in  diameter.     Inclosing  this  core  is  a  very  hard,  inner  bark 

7  Poi,  which  forms  an  important  part  of  the  native  diet,  is  made  from  taro,  which  for 
the  purpose  is  peeled,  cooked,  mashed,  pounded,,  and  then  allowed  to  ferment  slightly. 

8  .Tour.  Biol.  Chem.,  52  (1922),  No.  1,  p.  259.  Digestibility  of  raw  rice,  arrowroot,, 
canna.  cassava,  taro,  tree-fern,  and  potato  starches. 


14  BULLETIN  53,  HAWAII  EXPERIMENT  STATION 

varying  from  one-fourth  to  one-half  inch  in  thickness.  The  outer 
bark,  which  is  3  to  12  inches  thick,  is  made  up  of  coarse  roots. 
These  appear  as  air-feeding-  roots  attached  to  the  growing  frond 
which  die  and  form  a  part  of  the  outer  bark  of  the  trunk. 

An  examination  of  the  different  species  shows  that  Cibotium 
chamissoi  contains  a  relatively  large  starch  core  and  a  thin  exterior 
covering,  and  that  even  the  largest  specimens  of  G.  menziesii  con- 
tain a  small  core  and  a  very  thick  outer  bark  (PI.  VII,  fig.  1). 
Since  the  removal  of  the  bark  is  a  time-consuming  operation  at  best, 
G.  chamissoi  is  to  be  preferred,  of  the  two  varieties,  for  starch 
making,  because  it  has  a  larger  core  and  a  thinner  bark.  It  is  pref- 
erable also  because  it  contains  no  dextrins  and  other  material  which 
clog  the  shredding  machine  and  prevent  a  complete  sedimentation 
of  the  starch,  as  is  the  case  with  G.  menziesii.  The  other  species,  due 
to  their  small  size,  contain  cores  too  small  to  be  of  importance  for 
starch  production. 

The  first  operation  in  securing  the  starch  core  is  that  of  stripping 
off  the  outer  fibrous  bark  as  well  as  the  inner  shell.  The  bark  is 
slabbed  with  a  broad-bladed  ax  while  the  tree  is  standing,  the  work- 
man beginning  as  near  the  top  as  he  can  reach  and  working  down. 
As  much  as  possible  of  the  bark  is  removed  while  the  tree  stands. 
After  the  tree  has  been  felled,  the  remainder  of  the  bark  is  slabbed 
off.  The  core  appears  as  a  yellowish- white  log,  averaging  4  to  8 
inches  in  diameter,  3  to  10  feet  in  length,  and  30  to  100  pounds  in 
weight  (PL  VII,  fig.  2).  The  logs  are  then  carried  to  the  nearest 
road  by  donkeys  and  thence  to  the  mill  by  truck.  They  should  be 
milled  within  36  hours  after  cutting  to  avoid  hydrolysis  and  fer- 
mentation. Deterioration  will  not  be  so  rapid  if  the  inner  bark  is 
left  on  the  log,  but  the  already  heavy  cost  of  hauling  will  be  in- 
creased by  the  added  weight. 

Experiments  in  preserving  the  starch  log  under  water  were  not 
successful,  due  apparently  to  the  partial  hydrolysis  of  the  starch  into 
dextrins,  with  a  resultant  stickiness  that  interfered  materially  with 
the  process  of  extraction. 

A  skilled  workman,  felling  trees  averaging  50  pounds  to  the  starch 
core,  should  be  able  to  cut  about  1,000  pounds  a  day.  Only  4  or  5 
tons  of  starch  core  can  be  cut  from  an  acre  of  G.  chamissoi,  since  the 
mature  trees  alone  are  used  for  starch  production. 

Upon  its  arrival  at  the  mill  the  starch  core  is  cleansed  of  adhering 
soil  and  bark  chips.  It  is  then  reduced  to  pulp  by  means  of  a  power 
shredder.  The  shredder  used  in  this  investigation  consists  of  a 
cylinder  of  sheet  iron  which  has  been  fitted  on  a  wooden  core  and 
given  a  roughened  surface  by  having  the  perforations  punched 
through  from  the  inside.  Water  is  used  copiously  during 
the  shredding  process  to  prevent  the  cylinder  from  becoming  coated. 
The  pulp  is  then  run  into  a  revolving  screen,  where  it  is  sprayed  with 
fresh  water.  The  screen  has  a  tendency  to  agitate  and  contains  on 
its  inner  surface  wooden  cleats  which  facilitate  washing  the  pulp 
free  from  starch.  The  milky  starch  water  is  run  into  wooden  tanks 
of  about  500-gallons  capacity,  and  the  starch  is  purified  by  sedi- 
mentation. The  wet.  purified  starch  is  then  put  into  sugar  centri- 
fuges, which  remove  a  considerable  part  of  the  water  at  much  less 
cost   than   would   be    involved   in    drying  the   starch   by   heat.     A 


HAWAIIAN  TREE  FERN  AS  A  SOURCE  OF  STARCH  15 

rotary  starch  drier  removes  the  remainder  of  the  water.     The  dried 
starch  is  then  powdered  and  put  into  1-pound  packages  for  market. 

COST   OF  THE  RAW  MATERIAL 

Strange  as  it  may  seem,  the  cost  per  ton  of  landing  the  starch 
core  at  the  mill  is  greater  than  is  the  cost  of  production  of  most 
of  the  common  starch  crops  in  Hawaii.  The  following  prices  per 
ton  prevail  for  landing  the  raw  material  at  the  mill  at  Hilo,  Hawaii, 
from  the  tract  located  4  miles  north  of  the  Volcano  Road  at  18  Miles : 
Cutting  and  stripping  logs  $6.50,  making  donkey  trails  and  carrving 
logs  to  road  $1,  trucking  to  Hilo  $3.50,  total  $11. 

The  first  item  is  a  fixed  cost  and  could  not  be  materially  changed 
at  the  present  wage  scale  in  Hawaii.  The  making  of  donkey  trails 
would  increase  in  cost  as  it  became  necessary  to  exploit  more  remote 
areas;  and  shipping  by  rail  to  Hilo  would  not  materially  cheapen 
transportation  charges  since  the  main  difficulty  lies  in  getting  the 
material  from  the  forests  to  the  main  road.  It  is  apparent,  there- 
fore, that  the  above  listed  items  can  not  well  be  reduced  under  pres- 
ent conditions. 

FUTURE  OF  THE  INDUSTRY 

The  development  of  the  tree-fern  starch  industry  in  Hawaii  is 
seriously  handicapped  by  the  high  cost  of  the  raw  material  (starch 
core) ,  and  the  very  slow  rate  of  growth  of  the  tree  which  makes  it 
impracticable  to  establish  a  permanent  starch-producing  area.  The 
industry  might  become  permanently  established  in  Hawaii  by  mar- 
keting "the  starch  as  a  special-purpose  starch  rather  than  in  direct 
competition  with  cornstarch  as  a  food,  or  with  potato  starch  for  in- 
dustrial uses.  The  amount  used  for  special  purposes  would,  of 
course,  be  limited,  but  the  market  price  could  be  placed  sufficiently 
high  to  compensate  for  the  high  cost  of  raw  material. 

In  considering  the  possibilities  of  this  industry  in  other  tropical 
countries,  it  is  important  to  bear  in  mind  that  a  very  large  per- 
centage of  the  total  cost  of  production  is  for  labor.  Only  a  small 
capital  is  required  to  start  the  industry.  The  tree-fern  lands  are 
usually  of  very  little  value  for  any  other  purpose,  and  can  be  leased 
at  a  nominal  rental;  and  the  starch  extraction  machinery  is  rela- 
tively inexpensive.  The  actual  starch  extraction  process  costs  less 
than  a  cent  a  pound  of  finished  product.  It  is  evident,  therefore, 
that  in  countries  where  labor  costs  are  only  a  fraction  of  what  they 
are  in  Hawaii  the  cost  of  producing  tree-fern  starch  could  be  greatly 
reduced  and  might  well  be  brought  to  a  sufficiently  low  figure  to  per- 
mit of  commercial  production.  This  is,  of  course,  based  on  the 
assumption  that  the  species  of  tree  ferns  found  elsewhere  are  equally 
as  well  adapted  to  starch  production  as  is  Cibotiwn  chamissoi. 

SUMMARY 

The  Hawaiian  Islands  contain  many  thousands  of  acres  of  tree- 
fern  forests  from  which  starch  can  be  extracted. 

Three  species  are  found  in  Hawaii,  only  one  of  which,  Hapu 
{Ciootium  chamissoi) ,  is  used  for  starch  production. 


16  BULLETIN  53,  HAWAII  EXPERIMENT  STATION 

Experiments  in  propagation  of  the  tree  fern  show  that  not  only 
the  crowns,  but  also  the  large  and  the  small  lateral  shoots,  and  un- 
developed buds  on  the  trunk,  may  be  successfully  planted.  An  aver- 
age of  three  plantings  or  sets  can  be  secured  from  each  mature  tree 
fern. 

The  station  developed  a  method  for  determining  the  rate  of  growth 
of  the  tree  fern.  This  method  showed  the  vertical  growth  to  be  only 
4.35  inches  a  year,  which  means  that  it  would  require  20  years  for  a 
tree  fern  to  reach  sufficient  size  for  starch  production.  Such  a  slow 
rate  of  growth  makes  it  commercially  impracticable  to  plant  cut- 
tings from  different  parts  of  the  tree  fern,  or  to  build  permanent 
roads  or  fences  for  the  purpose  of  obtaining  the  raw  material. 

The  high  costs  involved  in  securing  raw  material  preclude  the 
possibility  of  the  starch  becoming  a  competitor  with  the  common 
commercial  starches,  and  likewise  limit  its  use  to  special  purposes 
commanding  a  high  market  price.  With  the  cheap  labor  available 
in  many  of  the  tropical  countries,  however,  the  costs  could  be  re- 
duced to  a  fraction  of  what  they  are  in  Hawaii. 

In  chemical  composition  the  core  of  the  tree  fern  is  similar  to  that 
of  other  starch  crops,  especially  of  edible  canna. 

Morphologically,  the  starches  of  the  different  species  of  tree  ferns 
are  very  similar,  differing  chiefly  in  size,  but  also  somewhat  in  shape. 

Tree-fern  starch  is  used  both  as  a  food  and  for  laundry  purposes. 
It  is  markedly  superior  to  cornstarch  for  laundry  purposes.  In  Ha- 
waii the  starch  is  used  chiefly  in  the  preparation  of  poi. 

Although  the  development  of  the  tree-fern  starch  industry  is 
seriously  handicapped  by  the  high  cost  of  securing  the  raw  material, 
data  have  been  secured  which  would  make  possible,  in  cases  of 
emergency,  the  production  on  short  notice  of  sufficient  starch  to  meet 
the  need  of  the  local  population. 


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